Medical devices for modulating nerves

ABSTRACT

Medical devices and methods for making and using medical devices are disclosed. An example medical device may include a medical device for modulating nerves. The medical device may include an elongate shaft having a distal region. A balloon may be coupled to the distal region. An electrode may be disposed within the balloon. A virtual electrode may be defined on the balloon. The virtual electrode may include a conductive region having an edge and a peripheral region disposed at least partially along the edge of the conductive region. The peripheral region may be configured to dissipate forces, electrical current, or both accumulating along the edge of the conductive region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 to U.S.Provisional Application Ser. No. 61/776,637, filed Mar. 11, 2013, theentirety of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure pertains to medical devices, and methods formanufacturing medical devices. More particularly, the present disclosurepertains to elongated medical devices for modulating nerves.

BACKGROUND

A wide variety of intracorporeal medical devices have been developed formedical use, for example, intravascular use. Some of these devicesinclude guidewires, catheters, and the like. These devices aremanufactured by any one of a variety of different manufacturing methodsand may be used according to any one of a variety of methods. Of theknown medical devices and methods, each has certain advantages anddisadvantages. There is an ongoing need to provide alternative medicaldevices as well as alternative methods for manufacturing and usingmedical devices.

BRIEF SUMMARY

This disclosure provides design, material, manufacturing method, and usealternatives for medical devices. An example medical device may includea medical device for modulating nerves. The medical device may includean elongated shaft having a distal region. A balloon may be coupled tothe distal region. An electrode may be disposed within the balloon. Avirtual electrode may be defined on the balloon. The virtual electrodemay include a conductive region having an edge and a peripheral regiondisposed at least partially along the edge of the conductive region. Theperipheral region may be configured to dissipate forces, electricalcurrent, or both accumulating along the edge of the conductive region.

An example method for manufacturing a medical device may includeproviding an expandable balloon, disposing a first mask member on theballoon, disposing a second mask member on the balloon adjacent to thefirst mask member, coating the balloon with a non-conductive material,and removing the first mask and the second mask from the balloon todefine a virtual electrode.

Another example method for manufacturing a medical device may includeproviding an expandable balloon, disposing a first mask member on theballoon, disposing a second mask member on the balloon adjacent to thefirst mask member, coating the balloon with a non-conductive material,removing the first mask member from the balloon, recoating the balloon,and removing the second mask from the balloon to define a virtualelectrode. The virtual electrode may be defined along a first portion ofthe balloon corresponding to where the first mask was disposed andwherein a stepped edge region is defined along a second portion of theballoon corresponding to where the second mask was disposed. The methodmay also include providing a catheter shaft having an electrode coupledthereto and attaching the balloon the catheter shaft. The balloon may bedisposed about the electrode.

Another example method for manufacturing a medical device may includeproviding an expandable balloon and disposing a first mask member on theballoon. The first mask member may project radially from an outersurface of the balloon. The method may also include disposing a secondmask member on the balloon adjacent to the first mask member. At least aregion of the second mask member may be free from contact with the outersurface of the balloon. The method may also include coating the balloonwith a non-conductive material, removing the first mask member from theballoon, recoating the balloon, and removing the second mask from theballoon to define a virtual electrode. The virtual electrode may bedefined along a first portion of the balloon corresponding to where thefirst mask was disposed and wherein a feathered, or tapered insulationcoating thickness, edge region is defined along a second portion of theballoon corresponding to where the second mask was disposed. The methodmay also include providing a catheter shaft having an electrode coupledthereto and attaching the balloon the catheter shaft. The balloon may bedisposed about the electrode.

An example balloon catheter for modulating renal nerves may include anelongate catheter shaft having a distal region. A balloon may be coupledto the distal region. The balloon may include an inner conductive layer,an outer insulating layer, and an intermediate layer disposed betweenthe inner conductive layer and the outer insulating layer. An electrodemay be coupled to the catheter shaft and may be disposed within theballoon. A virtual electrode may be defined on the balloon. The virtualelectrode may include a conductive region and an edge region disposed atleast partially along the conductive region. The conductive region mayinclude the inner conductive layer. In addition, the conductive regionmay be free of the intermediate layer and may be free of the outerinsulating layer. The edge region may include the inner conductive layerand the intermediate layer. In addition, the edge region may include theintermediate layer and may be free of the outer insulating layer.

The above summary of some embodiments is not intended to describe eachdisclosed embodiment or every implementation of the present disclosure.The Figures, and Detailed Description, which follow, more particularlyexemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing detailed description in connection with the accompanyingdrawings, in which:

FIG. 1 is a schematic view illustrating a renal nerve modulation systemin situ;

FIG. 2 is a side view of a portion of an example medical device;

FIG. 3 is a cross-sectional view taken through line 3-3 in FIG. 2;

FIG. 4 is a cross-sectional view taken through line 4-4 in FIG. 2;

FIGS. 5-11 illustrate some portions of an example method formanufacturing a medical device;

FIG. 12 is a partial cross-sectional view of an example medical device;

FIGS. 13-14 illustrate some portions of another example method formanufacturing a medical device; and

FIGS. 15-17 illustrate some portions of another example method formanufacturing a medical device.

While the disclosure is amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the invention tothe particular embodiments described. On the contrary, the intention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the disclosure.

DETAILED DESCRIPTION

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification.

All numeric values are herein assumed to be modified by the term“about,” whether or not explicitly indicated. The term “about” generallyrefers to a range of numbers that one of skill in the art would considerequivalent to the recited value (i.e., having the same function orresult). In many instances, the terms “about” may include numbers thatare rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numberswithin that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and5).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

It is noted that references in the specification to “an embodiment”,“some embodiments”, “other embodiments”, etc., indicate that theembodiment described may include one or more particular features,structures, and/or characteristics. However, such recitations do notnecessarily mean that all embodiments include the particular features,structures, and/or characteristics. Additionally, when particularfeatures, structures, and/or characteristics are described in connectionwith one embodiment, it should be understood that such features,structures, and/or characteristics may also be used connection withother embodiments whether or not explicitly described unless clearlystated to the contrary.

The following detailed description should be read with reference to thedrawings in which similar elements in different drawings are numberedthe same. The drawings, which are not necessarily to scale, depictillustrative embodiments and are not intended to limit the scope of theinvention.

Certain treatments require the temporary or permanent interruption ormodification of select nerve function. One example treatment is renalnerve ablation, which is sometimes used to treat conditions related tohypertension and/or congestive heart failure. The kidneys produce asympathetic response to congestive heart failure, which, among othereffects, increases the undesired retention of water and/or sodium.Ablating some of the nerves running to the kidneys may reduce oreliminate this sympathetic function, which may provide a correspondingreduction in the associated undesired symptoms.

While the devices and methods described herein are discussed relative torenal nerve modulation, it is contemplated that the devices and methodsmay be used in other treatment locations and/or applications where nervemodulation and/or other tissue modulation including heating, activation,blocking, disrupting, or ablation are desired, such as, but not limitedto: blood vessels, urinary vessels, or in other tissues via trocar andcannula access. For example, the devices and methods described hereincan be applied to hyperplastic tissue ablation, cardiac ablation,pulmonary vein isolation, tumor ablation, benign prostatic hyperplasiatherapy, nerve excitation or blocking or ablation, modulation of muscleactivity, hyperthermia or other warming of tissues, etc. In someinstances, it may be desirable to ablate perivascular renal nerves withultrasound ablation.

FIG. 1 is a schematic view of an illustrative renal nerve modulationsystem in situ. System 10 may include one or more conductive element(s)16 for providing power to a renal ablation system including a renalnerve modulation device 12 and, optionally, within delivery sheath orguide catheter 14. A proximal end of conductive element(s) 16 may beconnected to a control and power unit 18, which may supply theappropriate electrical energy to activate one or more electrodesdisposed at or near a distal end of the renal nerve modulation device12. In addition, control and power unit 18 may also be utilized tosupply/receive the appropriate electrical energy and/or signal toactivate one or more sensors disposed at or near a distal end of therenal nerve modulation device 12. When suitably activated, theelectrodes are capable of ablating tissue as described below and thesensors may be used to sense desired physical and/or biologicalparameters. The terms electrode and electrodes may be considered to beequivalent to elements capable of ablating adjacent tissue in thedisclosure which follows. In some instances, return electrode patches 20may be supplied on the legs or at another conventional location on thepatient's body to complete the circuit. A proximal hub (not illustrated)having ports for a guidewire, an inflation lumen and a return lumen mayalso be included.

The control and power unit 18 may include monitoring elements to monitorparameters such as power, voltage, pulse size, temperature, force,contact, pressure, impedance and/or shape and other suitable parameters,with sensors mounted along renal nerve modulation device 12, as well assuitable controls for performing the desired procedure. In someembodiments, the power unit 18 may control a radiofrequency (RF)electrode and, in turn, may “power” other electrodes including so-called“virtual electrodes” described herein. The electrode may be configuredto operate at a suitable frequency and generate a suitable signal. It isfurther contemplated that other ablation devices may be used as desired,for example, but not limited to resistance heating, ultrasound,microwave, and laser devices and these devices may require that power besupplied by the power unit 18 in a different form.

FIG. 2 illustrates a distal portion of a renal nerve modulation device12. Here it can be seen that renal nerve modulation device 12 mayinclude an elongate member or catheter shaft 34, an expandable member orballoon 22 coupled to shaft 34, and an electrode 24 disposed withinballoon 22. Additional electrodes 24 may also be utilized. When in use,balloon 22 may be filled with a conductive fluid such as saline to allowthe ablation energy (e.g., radiofrequency energy) to be transmitted fromelectrode 24, through the conductive fluid, to one or more windows 28disposed along balloon 22. While saline is one example conductive fluid,other conductive fluids may also be utilized including hypertonicsolutions, contrast solution, mixtures of saline or hypertonic salinesolutions with contrast solutions, and the like. The conductive fluidmay be introduced through a fluid inlet 31 and evacuated through a fluidoutlet 32. This may allow the fluid to be circulated within balloon 22.As described in more detail herein, windows 28 may be generallyhydrophilic portions of balloon 22. Accordingly, windows 28 may absorbfluid (e.g., the conductive fluid) so that energy exposed to theconductive fluid can be conducted to windows 28 such that windows 28 totake the form of “virtual electrodes” capable of ablating tissue.

A cross-sectional view of shaft 34 of the renal nerve modulation device12 proximal to balloon 22 is illustrated in FIG. 3. Here it can be seenthat shaft 34 may include a guidewire lumen 36, a lumen 38 connected tothe fluid inlet 31, and a lumen 40 connected to the fluid outlet 32.Other configurations are contemplated. In some embodiments, guidewirelumen 36 and/or one of the fluid lumens 38/40 may be omitted. In someembodiments, guidewire lumen 36 may extend from the distal end of device12 to a proximal hub. In other embodiments, the guidewire lumen can havea proximal opening that is distal the proximal portion of the system. Insome embodiments, the fluid lumens 38/40 can be connected to a system tocirculate the fluid through the balloon 22 or to a system that suppliesnew fluid and collects the evacuated fluid. It can be appreciated thatembodiments may function with merely a single fluid lumen and a singlefluid outlet into the balloon.

Electrode 24 (or a conductive element to supply power to electrode 24)may extend along the outer surface of shaft 34 or may be embedded withinthe shaft. Electrode 24 proximal to the balloon may be electricallyinsulated and may be used to transmit power to the portion of theelectrode 24 disposed within balloon 22. Electrode 24 may be a flatribbon electrode made from platinum, gold, stainless steel, cobaltalloys, or other non-oxidizing materials. In some instances, titanium,tantalum, or tungsten may be used. Electrode 24 may extend alongsubstantially the whole length of the balloon 22 or may extend only asfar as the distal edge of the most distal window 28. The electrode 24may have a generally helical shape and may be wrapped around shaft 34.Alternatively, electrode 24 may have a linear or other suitableconfiguration. In some cases, electrode 24 may be bonded to shaft 34.The electrode 24 and windows 28 may be arranged so that the electrodeextends directly under the windows 28. In some embodiments, electrode 24may be a wire or may be a tubular member disposed around shaft 34. Insome embodiments, a plurality of electrodes 24 may be used and each ofthe plurality may be fixed to the shaft 34 under windows 28 and mayshare a common connected to conductive element 16. In other embodimentsthat include more than one electrode, each electrode may be separatelycontrollable. In such embodiments, balloon 22 may be partitioned intomore than one chamber and each chamber may include one or moreelectrodes. The electrode 24 may be selected to provide a particularlevel of flexibility to the balloon to enhance the maneuverability ofthe system. It can be appreciated that there are many variationscontemplated for electrode 24.

A cross-sectional view of the shaft 34 distal to fluid outlet 32 isillustrated in FIG. 4. The guidewire lumen 36 and the fluid inlet lumen40 are present, as well as electrode 24. In addition, balloon 22 isshown in cross-section as having a first layer 44 and a second layer 46.Window 28 is formed in balloon 22 by the absence of second layer 46.First layer 44 may include a hydrophilic, hydratable, RF permeable,and/or conductive material. One example material is a hydrophilicpolyurethane (e.g., TECOPHILIC® TPUs such as TECOPHILIC® HP-60D-60 andmixtures thereof, commercially available from the Lubrizol Corporationin Wickliffe, Ohio). Other suitable materials include other hydrophilicpolymers such as hydrophilic polyether block amide (e.g., PEBAX® MV1074and MH1657, commercially available from Arkema headquartered in King ofPrussia, Pa.), hydrophilic nylons, hydrophilic polyesters, blockco-polymers with built-in hydrophilic blocks, polymers including ionicconductors, polymers including electrical conductors, metallic ornanoparticle filled polymers, and the like. Suitable hydrophilicpolymers may exhibit between 20% to 120% hydrophilicity (or % waterabsorption). In at least some embodiments, first layer 44 may include ahydratable polymer that is blended with a non-hydratable polymer such asa non-hydratable polyether block amide (e.g., PEBAX®7033 and 7233,commercially available from Arkema) and/or styrenic block copolymerssuch as styrene-isoprene-styrene. These are just examples.

The second layer 46 may include an electrically non-conductive polymersuch as a non-hydrophilic polyurethane, homopolymeric and copolymericpolyurethanes (e.g., NeoRez R-967, commercially available fromNeoResins, Inc. in Wilmington, Mass.; and/or TECOFLEX® SG-85A and/orTECOFLEX SG-60D, commercially available from Lubrizol Corp. inWickliffe, Ohio), polyether block amide, nylon, polyester orblock-copolymer. Other suitable materials include any of a range ofelectrically non-conductive polymers. These are just examples.

The materials of the first layer and the second layer may be selected tohave good bonding characteristics between the two layers. For example, aballoon 22 may be formed from a first layer 44 made from a hydrophilicpolyether block amide and a second layer 46 made from a regular ornon-hydrophilic polyether block amide. In other embodiments, a suitabletie layer (not illustrated) may be provided between the two layers.These are just examples.

Prior to use, balloon 22 may be hydrated as part of the preparatorysteps. Hydration may be effected by soaking the balloon in a salinesolution. During ablation, a conductive fluid may be infused intoballoon 22, for example via outlet 32. The conductive fluid may expandthe balloon to the desired size. The balloon expansion may be monitoredindirectly by monitoring the volume of conductive fluid introduced intothe system or may be monitored through radiographic or otherconventional means. Optionally, once the balloon is expanded to thedesired size, fluid may be circulated within the balloon by continuingto introduced fluid through the fluid inlet 31 while withdrawing fluidfrom the balloon through the fluid outlet 32. The rate of circulation ofthe fluid may be between 2 and 20 ml/min, between 3 and 15 ml/min,between 5 and 10 ml/min or other desired rate of circulation. These arejust examples. The circulation of the conductive fluid may mitigate thetemperature rise of the tissue of the blood vessel in contact with thewindows 28.

Electrode 24 may be activated by supplying energy to electrode 24. Theenergy may be supplied at 400-500 KHz at about 5-30 watts of power.These are just examples, other energies are contemplated. The energy maybe transmitted through the medium of the conductive fluid and throughwindows 28 to the blood vessel wall to modulate or ablate the tissue.The second layer 46 of the balloon prevents the energy transmissionthrough the balloon wall except at windows 28 (which lack second layer46).

Electrode 24 may be activated for an effective length of time, such as 1minute or 2 minutes. One the procedure is finished at a particularlocation, balloon 22 may be partially or wholly deflated and moved to adifferent location such as the other renal artery, and the procedure maybe repeated at another location as desired using conventional deliveryand repositioning techniques.

When expanding a multilayer balloon where a portion of one layer of theballoon is absent (e.g., defining a “window”) may tend to concentratestress and/or forces on the balloon adjacent to the window. This mayinclude the concentration of forces along the edge or periphery of aballoon window. Repeated expansion of the balloon could lead to stresson the balloon and, potentially, balloon failure. In addition, currenttransmitted to a discrete balloon region such as a balloon window mayalso tend to accumulate along the edge of the window. This accumulationof current may lead to temperature increases along the window edge,which could also reduce the long-term resiliency of the balloon.

Disclosed herein are medical devices, balloons, and methods for makingthe same where one or more discrete balloon “conductive windows” or“virtual electrodes” are defined. The virtual electrodes are designed todissipate or otherwise help to spread out forces that may tend toaccumulate along the edge of the window. In addition, the virtualelectrodes may also help to more evenly distribute or otherwise spreadcurrent so that current accumulation along the edge of the window canalso be reduced. Some of these and other features are described in moredetail herein.

In at least some embodiments, a “dual mask” manufacturing process may beutilized to manufacture a balloon 122 as shown schematically in FIGS.5-11. In general, the process may result in balloon 122 having a taperedor stepped edge along the periphery of the balloon windows. The steppededge may aid in distributing forces and/or current that may accumulateadjacent the window edge. In the schematic drawings, other portions ofthe catheter or medical device that includes balloon 122 may also beseen. The other portions of the devices may or may not be present duringthe manufacturing process. The intent of showing these structures in thedrawings is to demonstrate that balloon 122 may be used with medicaldevices such as those disclosed herein. In addition, balloon 122 may beutilized in medical devices such as device 12 (and/or other devicesdisclosed herein). Accordingly, the structural features of balloon 122may be incorporated into device 12 (and/or other devices disclosedherein).

FIG. 5 is a side view of a portion of an example balloon 122. Balloon122 may include a base or inner layer 144. In at least some embodiments,inner layer 144 may include a hydrophilic and/or conductive materialsuch as those materials disclosed herein. A first mask member 148 may bedisposed on inner layer 144. First mask member 148 may vary but in someembodiments may include a masking tape or other suitable maskingmaterial. A second mask member 150 may be disposed adjacent to firstmask member 148 as shown in FIG. 6. This may include disposing secondmask member 150 over or on top of first mask member 148 (which isschematically illustrated by showing first mask member 148 in phantomline). Alternatively, first mask member 148 and second mask member 150may be formed from single member that can be separated into multiplepieces. For example, first mask member 148 and second mask member 150may be discrete portions of a single “mask” that are separated by aperforation or line of weakness (which may be schematically representedby the phantom line between mask members 148/150 in FIG. 6). Such aconfiguration may allow mask members 148/150 to be applied collectivelyto balloon 122 in a single step and to be removed independently from oneanother by tearing or otherwise separating mask members 148/150 alongthe perforation.

With mask members 148/150 in place, a coating 146 may be applied ontoballoon 122 (e.g., onto inner layer 144) as shown in FIG. 7. In at leastsome embodiments, coating 146 may be applied by spray coating. Othermethods may also be used including dip coating or the like. Coating 146may include an electrically non-conductive and/or non-hydrophilicmaterial such as those disclosed herein. After application of coating146, mask member 150 may be removed, exposing a peripheral region 152corresponding to area covered by second mask member 150 but not firstmask member 148 as shown in FIG. 8. Subsequently, one or more additionalcoating processes may be performed. For example, a second coating 154may be applied onto balloon 122 (e.g., onto coating 146) as shown inFIG. 9. Coating 154 may also include an electrically non-conductiveand/or non-hydrophilic material such as those disclosed herein and mayor may not be the same material as coating 146. After application ofcoating 154, first mask member 148 may be removed, exposing an electrodeor conductive region 128 as shown in FIG. 10.

The process described above may result in a “stepped edge” or “taperededge” adjacent to conductive region 128. For example, the application ofcoating 154 may cover all of coating 146 and then extend onto peripheralregion 152 as shown in FIG. 11. Thus, a stepped edge to conductiveregion 128 may be formed at peripheral region 152 (e.g., by the presenceof coating 154 along with the absence of coating 146). Because onlycoating 146 may be present on inner layer 144 along peripheral region152, peripheral region 152 may have less resistance to expansion orstretching than other portions of balloon 122 including both coatings146/154. In other words, the thickness of the outer insulating layer ofballoon 122 (which may include both coatings 146/154) may vary orotherwise define a thickness gradient adjacent to the perimeter ofconductive region 128. Because of this, peripheral region 152 may helpto spread out forces that may be present along the edge of conductiveregion 128. Peripheral region 152 may also help to dissipate currentpresent along the edge of conductive region 128.

Numerous variations are contemplated for the process described above.For example, the shape, position, and/or configuration of mask members148/150 may vary. For example, one or both of mask members 148/150 mayhave a circular, oval, polygonal, irregular, or other shape. Thethicknesses, material composition, and other features of coatings146/154 may also vary. In some embodiments, additional mask members maybe utilized to form one or more additional conductive regions 128. Inaddition, additional masks and/or coating steps may also be performed.For example, FIG. 12 illustrates balloon 122′ that may be formed usingthree masks and includes a third coating 156 that may cover all ofcoating 154 and may include a first peripheral portion 158 a thatextends onto and covers peripheral region 152 and then a secondperipheral portion 158 b that extends onto inner layer 144. This is justan example. Other variations are contemplated.

In use, balloon 122 may be used in a manner similar to balloon 22. Forexample, balloon 122 may be attached to catheter shaft such as cathetershaft 34 and used for a suitable intervention such as an ablationprocedure. During ablation, a conductive fluid may be infused intoballoon 122 and an electrode positioned within balloon 122 (e.g.,electrode 24) may be activated. The energy may be transmitted throughthe medium of the conductive fluid and through conductive region 128 tothe blood vessel wall to modulate or ablate the tissue. Coatings 146/154may prevent the energy transmission through the balloon wall atlocations other than conductive region 128. In some embodiments, arelatively small amount of energy may be transmitted along peripheralregion 152 due to the presence of a smaller amount of insulatingmaterial along peripheral region 152. This may help improve currentdistribution.

FIG. 13 illustrates another example balloon 222 and the process formanufacturing balloon 222. In at least some embodiments, first mask 248may be disposed on inner layer 244 of balloon 222. First mask 248 mayprotrude from the surface of balloon 22 (e.g., may project radially frominner layer 244). Second mask 250 may be positioned on first mask 248.Because first mask 248 may project radially outward from inner layer244, portions of second mask 250 such as edge portions 260 may not besecured to or otherwise be in contact with balloon 222. Accordingly, theapplication of coating 246 (e.g., via spray coating, dip coating, or thelike) may result in parts of coating 246 migrating under edge portions260 of second mask 250 and define a smooth tapering or “feathered” edge252 adjacent to window or conductive region 228 as shown in FIG. 14.This featured edge adjacent to conductive region may help to spread outforces that may be present along the edge of conductive region 228 andmay also help to dissipate current present along the edge of conductiveregion 228.

FIG. 15 illustrates another example balloon 322 having inner layer 344.First mask member 348 and second mask member 350 may be disposed onballoon 322. In this example, first mask member 348 may be disposed oninner layer 344 and second mask member 350 may be disposed on first maskmember 348. Other configurations are contemplated.

Inner layer 344 may be subjected to a surface treatment that may aid inadhering additional layers or material thereto. For example, a portionof balloon 322 may include a plasma treated region 362. In general,plasma treated region 362 may be defined by plasma treating portion(s)of balloon 322. This may include developing or otherwise defining anappropriate plasma treatment cycle that provides the desired adhesionsufficient to define adhesion differences from non-treated regions. Someexample parameters for plasma treatment are provided in Table 1 below.

TABLE 1 Setting Recipe A Recipe B Recipe C Gas Helium Oxygen Argon Power(W) 600 600 400 Gas flow 350 600 150 (SCCM) Time (s) 360  60  60 PlateGround Powered Powered Plate spacing Top plate: slot 2 Top plate: slot 2Top plate: slot 2 (count from Bottom plate: 11 Bottom plate: 11 Bottomplate: 11 top) Base Pressure 100 100 100 (mT)

After plasma treatment, second mask member 350 may be removed andcoating 346 may be applied to balloon 322 as shown in FIG. 16. Firstmask member 348 may then be removed from balloon 322 to define window orconductive region 328 as shown in FIG. 17. Due to plasma treatment,coating 346 may adhere to inner layer 344 along plasma treated region362. A peripheral region 352 of coating 346 may defined a “non-adhered”or “less-adhered” region. The non-adhered peripheral region 352 may helpto diffuse and distribute mechanical, electrical, heat-induced or otherforces that may be present along the edge of conductive region 328 andmay also help to dissipate current present along the edge of conductiveregion 328.

The materials that can be used for the various components of device 12(and/or other medical devices disclosed herein) may include thosecommonly associated with medical devices. For simplicity purposes, thefollowing discussion makes reference to device 12. However, this is notintended to limit the devices and methods described herein, as thediscussion may be applied to other similar medical devices disclosedherein.

Device 12 may be made from a metal, metal alloy, polymer (some examplesof which are disclosed below), a metal-polymer composite, ceramics,combinations thereof, and the like, or other suitable material. Someexamples of suitable metals and metal alloys include stainless steel,such as 304V, 304L, and 316LV stainless steel; mild steel;nickel-titanium alloy such as linear-elastic and/or super-elasticnitinol; other nickel alloys such as nickel-chromium-molybdenum alloys(e.g., UNS: N06625 such as INCONEL® 625, UNS: N06022 such as HASTELLOY®UNS: N10276 such as HASTELLOY® C276®, other HASTELLOY® alloys, and thelike), nickel-copper alloys (e.g., UNS: N04400 such as MONEL® 400,NICKELVAC® 400, NICORROS® 400, and the like),nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such asMP35-N® and the like), nickel-molybdenum alloys (e.g., UNS: N10665 suchas HASTELLOY® ALLOY B2®), other nickel-chromium alloys, othernickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-ironalloys, other nickel-copper alloys, other nickel-tungsten or tungstenalloys, and the like; cobalt-chromium alloys; cobalt-chromium-molybdenumalloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like);platinum enriched stainless steel; titanium; combinations thereof; andthe like; or any other suitable material.

As alluded to herein, within the family of commercially availablenickel-titanium or nitinol alloys, is a category designated “linearelastic” or “non-super-elastic” which, although may be similar inchemistry to conventional shape memory and super elastic varieties, mayexhibit distinct and useful mechanical properties. Linear elastic and/ornon-super-elastic nitinol may be distinguished from super elasticnitinol in that the linear elastic and/or non-super-elastic nitinol doesnot display a substantial “superelastic plateau” or “flag region” in itsstress/strain curve like super elastic nitinol does. Instead, in thelinear elastic and/or non-super-elastic nitinol, as recoverable strainincreases, the stress continues to increase in a substantially linear,or a somewhat, but not necessarily entirely linear relationship untilplastic deformation begins or at least in a relationship that is morelinear that the super elastic plateau and/or flag region that may beseen with super elastic nitinol. Thus, for the purposes of thisdisclosure linear elastic and/or non-super-elastic nitinol may also betermed “substantially” linear elastic and/or non-super-elastic nitinol.

In some cases, linear elastic and/or non-super-elastic nitinol may alsobe distinguishable from super elastic nitinol in that linear elasticand/or non-super-elastic nitinol may accept up to about 2-5% strainwhile remaining substantially elastic (e.g., before plasticallydeforming) whereas super elastic nitinol may accept up to about 8%strain before plastically deforming. Both of these materials can bedistinguished from other linear elastic materials such as stainlesssteel (that can also can be distinguished based on its composition),which may accept only about 0.2 to 0.44 percent strain beforeplastically deforming.

In some embodiments, the linear elastic and/or non-super-elasticnickel-titanium alloy is an alloy that does not show anymartensite/austenite phase changes that are detectable by differentialscanning calorimetry (DSC) and dynamic metal thermal analysis (DMTA)analysis over a large temperature range. For example, in someembodiments, there may be no martensite/austenite phase changesdetectable by DSC and DMTA analysis in the range of about −60 degreesCelsius (° C.) to about 120° C. in the linear elastic and/ornon-super-elastic nickel-titanium alloy. The mechanical bendingproperties of such material may therefore be generally inert to theeffect of temperature over this very broad range of temperature. In someembodiments, the mechanical bending properties of the linear elasticand/or non-super-elastic nickel-titanium alloy at ambient or roomtemperature are substantially the same as the mechanical properties atbody temperature, for example, in that they do not display asuper-elastic plateau and/or flag region. In other words, across a broadtemperature range, the linear elastic and/or non-super-elasticnickel-titanium alloy maintains its linear elastic and/ornon-super-elastic characteristics and/or properties.

In some embodiments, the linear elastic and/or non-super-elasticnickel-titanium alloy may be in the range of about 50 to about 60 weightpercent nickel, with the remainder being essentially titanium. In someembodiments, the composition is in the range of about 54 to about 57weight percent nickel. One example of a suitable nickel-titanium alloyis FHP-NT alloy commercially available from Furukawa Techno Material Co.of Kanagawa, Japan. Some examples of nickel titanium alloys aredisclosed in U.S. Pat. Nos. 5,238,004 and 6,508,803, which areincorporated herein by reference. Other suitable materials may includeULTANIUM™ (available from Neo-Metrics) and GUM METAL™ (available fromToyota). In some other embodiments, a superelastic alloy, for example asuperelastic nitinol can be used to achieve desired properties.

In at least some embodiments, portions or all of device 12 may also bedoped with, made of, or otherwise include a radiopaque material.Radiopaque materials are understood to be materials capable of producinga relatively bright image on a fluoroscopy screen or another imagingtechnique during a medical procedure. This relatively bright image aidsthe user of device 12 in determining its location. Some examples ofradiopaque materials can include, but are not limited to, gold,platinum, palladium, tantalum, tungsten alloy, polymer material loadedwith a radiopaque filler, and the like. Additionally, other radiopaquemarker bands and/or coils may also be incorporated into the design ofdevice 12 to achieve the same result.

In some embodiments, a degree of Magnetic Resonance Imaging (MRI)compatibility is imparted into device 12. For example, device 12 orportions thereof, may be made of a material that does not substantiallydistort the image and create substantial artifacts (i.e., gaps in theimage). Certain ferromagnetic materials, for example, may not besuitable because they may create artifacts in an MRI image. Device 12 orportions thereof, may also be made from a material that the MRI machinecan image. Some materials that exhibit these characteristics include,for example, tungsten, cobalt-chromium-molybdenum alloys (e.g., UNS:R30003 such as ELGILOY®, PHYNOX®, and the like),nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such asMP35-N® and the like), nitinol, and the like, and others.

Some examples of suitable polymers for device 12 may includepolytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE),fluorinated ethylene propylene (FEP), polyoxymethylene (POM, forexample, DELRIN® available from DuPont), polyether block ester,polyurethane (for example, Polyurethane 85A), polypropylene (PP),polyvinylchloride (PVC), polyether-ester (for example, ARNITEL®available from DSM Engineering Plastics), ether or ester basedcopolymers (for example, butylene/poly(alkylene ether) phthalate and/orother polyester elastomers such as HYTREL® available from DuPont),polyamide (for example, DURETHAN® available from Bayer or CRISTAMID®available from Elf Atochem), elastomeric polyamides, blockpolyamide/ethers, polyether block amide (PEBA, for example availableunder the trade name PEBAX®), ethylene vinyl acetate copolymers (EVA),silicones, polyethylene (PE), Marlex high-density polyethylene, Marlexlow-density polyethylene, linear low density polyethylene (for exampleREXELL®), polyester, polybutylene terephthalate (PBT), polyethyleneterephthalate (PET), polytrimethylene terephthalate, polyethylenenaphthalate (PEN), polyetheretherketone (PEEK), polyimide (PI),polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide(PPO), poly paraphenylene terephthalamide (for example, KEVLAR®),polysulfone, nylon, nylon-12 (such as GRILAMID® available from EMSAmerican Grilon), perfluoro(propyl vinyl ether) (PFA), ethylene vinylalcohol, polyolefin, polystyrene, epoxy, polyvinylidene chloride (PVdC),poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS50A), polycarbonates, ionomers, biocompatible polymers, other suitablematerials, or mixtures, combinations, copolymers thereof, polymer/metalcomposites, and the like.

It should be understood that this disclosure is, in many respects, onlyillustrative. Changes may be made in details, particularly in matters ofshape, size, and arrangement of steps without exceeding the scope of thedisclosure. This may include, to the extent that it is appropriate, theuse of any of the features of one example embodiment being used in otherembodiments. The invention's scope is, of course, defined in thelanguage in which the appended claims are expressed.

What is claimed is:
 1. A medical device for modulating nerves, themedical device comprising: an elongate shaft having a distal region; aballoon coupled to the distal region; an electrode disposed within theballoon; and one or more virtual electrodes defined on the balloon, thevirtual electrodes including a conductive region having an edge and aperipheral region disposed at least partially along the edge of theconductive region, the peripheral region being configured to dissipatephysical forces, electrical current, or both accumulating along the edgeof the conductive region; wherein the balloon includes an innerconductive layer, an outer non-conductive layer, and an intermediatenon-conductive layer disposed between the inner conductive layer and theouter non-conductive layer; wherein the conductive region is definedalong a first portion of the balloon that includes the inner conductivelayer, is free of the outer non-conductive layer, and is free of theintermediate non-conductive layer; and wherein the peripheral region isdefined along a second portion of the balloon that includes the innerconductive layer, includes the outer non-conductive layer, and is freeof the intermediate non-conductive layer.
 2. The medical device of claim1, wherein the balloon includes a plurality of intermediatenon-conductive layers disposed between the inner conductive layer andthe outer non-conductive layer.
 3. The medical device of claim 1,wherein the intermediate non-conductive layer has a substantiallyconstant thickness.
 4. The medical device of claim 1, wherein theintermediate non-conductive layer has a variable thickness along theperipheral region.
 5. The medical device of claim 1, herein the medicaldevice comprises a plurality of said virtual electrodes.
 6. The medicaldevice of claim 1, wherein the peripheral region completely surroundsthe conductive region.
 7. A medical device for modulating nerves, themedical device comprising: an elongate shaft having a distal region; aballoon coupled to the distal region; an electrode disposed within theballoon; and one or more virtual electrodes defined on the balloon, thevirtual electrodes including a conductive region having an edge and aperipheral region disposed at least partially along the edge of theconductive region, the peripheral region being configured to dissipatephysical forces, electrical current, or both accumulating along the edgeof the conductive region; wherein the balloon includes an innerconductive layer and an outer non-conductive layer; wherein the innerconductive layer is plasma treated along at least a portion thereof;wherein the conductive region is defined along a first portion of theballoon that includes the inner conductive layer and is free of theouter non-conductive layer; wherein the peripheral region is definedalong a second portion of the balloon that includes the inner conductivelayer and the outer non-conductive layer; and wherein the conductiveregion and the peripheral region are free of plasma treatment.
 8. Themedical device of claim 7, wherein the balloon includes an adheredregion where the inner conductive layer is adhered to the outernon-conductive layer and a non-adhered region wherein the innerconductive layer is not adhered to the outer non-conductive layer. 9.The medical device of claim 7, wherein the medical device comprises aplurality of said virtual electrodes.
 10. The medical device of claim 7,wherein the peripheral region completely surrounds the conductiveregion.
 11. The medical device of claim 7, wherein the balloon includesan adhered region in which the inner conductive layer is plasma treatedand is adhered to the outer non-conductive layer and a non-adheredregion in which the inner conductive layer is free of plasma treatmentand is not adhered to the outer non-conductive layer.
 12. A ballooncatheter for modulating renal nerves, the catheter comprising: anelongate catheter shaft having a distal region; a balloon coupled to thedistal region; wherein the balloon includes an inner conductive layer,an outer insulating layer, and an intermediate layer disposed betweenthe inner conductive layer and the outer insulating layer; an electrodecoupled to the catheter shaft and disposed within the balloon; one ormore virtual electrodes defined on the balloon, the virtual electrodesincluding a conductive region and an edge region disposed at leastpartially along the conductive region; wherein the conductive regionincludes the inner conductive layer, is free of the intermediate layer,and is free of the outer insulating layer; and wherein the edge regionincludes the inner conductive layer, includes the outer insulating layerand is free of the intermediate layer.
 13. The balloon catheter of claim12, wherein the medical device comprises a plurality of said virtualelectrodes.
 14. The balloon catheter medical device of claim 12, whereinthe edge region completely surrounds the conductive region.